This invention relates to a finish composition for polyester fiber for use in reinforcing rubber.
Polyester fiber, such as polyethylene terephthalate, has excellent physical and chemical properties, is mass produced industrially, and is used widely in many fields. It is a very suitable material for reinforcing rubber.
However, when compared with polyamide fibers such as nylon 6 and nylon 66, which are also typical industrial fibers, polyester fibers have a great shortcoming in that their adhesion to rubber is inferior.
In other words, polyamide fibers achieve very good adhesion to rubber simply by treating them with a resorcinol-formaldehyde rubber latex (RFL); in the case of polyester fibers, however, good adhesion cannot be achieved by this RFL treatment. Thus, in order to achieve high adhesion to rubber, it is necessary to carry out the parallel application of adhesive to the polyester either in the same bath as that for the RFL dip treatment or in another bath; the dip treatment requires a high temperature. High temperature causes decomposition and fuming of the finish composition; it also causes yarn properties to deteriorate which causes functional degradation and, thus a drop in the performance of the rubber products. Also, high temperature treatment wastes energy.
With this background, this invention provides a finish composition for polyester fibers for use in reinforcing rubber. Excellent adhesion to rubber is achieved at a dip treatment temperature which is 20.degree.-30.degree. C. lower than conventional treatment temperatures while satisfying the requirements of the oil portion in producing yarn.